This invention concerns the partial imaging of a substrate with superimposed layers of marking material in the form of a print pattern with substantially exact registration. This methodology can be used to manufacture vision control panels, especially glass printed with ceramic ink.
A vision control panel may be defined as a light permeable material imaged with a print pattern which subdivides the panel into a plurality of imaged areas and/or a plurality of non-imaged areas. The visual properties of the light permeable material are consequently amended and are typically also dependent upon the illumination conditions on either side of the panel.
One type of vision control panel is a panel comprising a sheet of light permeable material with a design or a single colour visible from one side of the panel which is not visible from the other side of the panel, the design or single colour being superimposed on or forming at least a part of an opaque xe2x80x9csilhouette patternxe2x80x9d which subdivides the panel into a plurality of opaque areas and/or a plurality of light permeable areas.
Vision control panels, typically comprising transparent materials partially imaged with a pattern of opaque marking material, are well known. U.S. Pat. No. 4,102,101 (Neilsen et al) discloses toughened glass having a pattern of white ceramic ink dots to form the walls of a squash court. By having relatively bright illumination inside the squash court and relative darkness outside, the wall surface is visible to the players and forms an adequate background against which to sight a squash ball, at the same time allowing visibility inside the court by spectators. This one-way effect is similar to that provided by net curtains or sheers. U.S. Pat. No. 4,321,778(Whitehead) discloses another type of one-way vision control panel for squash courts, having a layer of black dots, superimposed by white dots, the black dots improving the visibility into the court by spectators and TV cameras. Whitehead discloses in detail methods of manufacturing such panels using ceramic ink waterslide transfers. GB2 118 096 (Hill and Yule) discloses the protection of white on black dots and other patterns within plastic panels and methods of forming such white on black patterns. GB2 165 292 (Hill) discloses panels of transparent or translucent material having a design on one side not visible from the other side, the design being superimposed on or forming a part of a silhouette pattern. Eight basic methods are disclosed in GB2 165 292 of making such panels. Each of these eight method descriptions typically disclose several variations within each method, an example of each method 1-8 being illustrated in FIGS. 18-25, respectively, of GB2 165 292.
Another type of vision control panel is described in WO97/25213 (Hill) comprising a transparent or translucent sheet and a transparent or translucent xe2x80x9cbase patternxe2x80x9d of a different colour to the xe2x80x9cneutral backgroundxe2x80x9d of the sheet. Methods of imaging such panels are disclosed including the imaging of a plurality of projecting surfaces defining the base pattern. GB2 174 383 B (Easton and Slavin) discloses methods of decorating glass by means of waterslide transfer.
GB2 188 873 (Hill) discloses methods and uses for methods of printing superimposed layers with substantially exact registration, including the manufacture of printed circuits and membrane switches, and obtaining the desired colour rendering of ink on non-white substrates and certain backlit illuminated displays, together with fifteen improvements to security printing, labels and seals. These methods rely on the removal of unwanted ink from a printed substrate to leave layers in substantially exact registration.
JP333/78 (Kawai), WO97/15453 (Hill) and WO98/17480 (Hill and Godden) disclose other methods of partially imaging substrates, including the selective transfer of marking material to preformed or selectively predated substrate. WO97/47481 (Mueller and Bird) discloses many methods of partially imaging substrates by digital techniques including electrostatic and thermal transfer techniques.
Method 2 of GB2 165 292 discloses the use of a transfer to form a panel according to the invention and, in particular, the use of a ceramic ink transfer in which the design and silhouette pattern are incorporated into the transfer by xe2x80x9cmethod 1 or any other method,xe2x80x9d then transferred to glass, the ceramic ink then being fused into the glass during a toughening process. One xe2x80x9cother methodxe2x80x9d disclosed is method 8 in which a xe2x80x9cfilm material can be punched, burnt, laser cut or otherwise cut normally to achieve a perforated membrane of a grid, net or filigree type of silhouette pattern, the holes of whatever shape forming the transparent areas. The holes may be formed after printing or otherwise applying the required design xe2x80x9cblocked outxe2x80x9d or the required design may be produced after the holes have, been formed . . . xe2x80x9d Such perforated sheets or membranes imaged with a design may then be formed within or attached to a transparent sheet. Precision Studios of Stoke-on-Trent, UK, a division of Josiah Wedgwood and Sons Ltd. developed the method according to GB2165292 of first printing ceramic ink transfer carrier material, the transfer carrier material and the printed ceramic ink then being perforated together. Samples of toughened glass panels produced by such printed then perforated ceramic ink transfers were first made public bearing the Precision Studios""name in 1996. U.S. Pat. No. 5,830,529 (Ross) also discloses the method of perforating ceramic decals.
Other methods of utilising perforated materials to form partially imaged panels according to GB2 165 292, for example, for advertising on the windows of buses, taxis and retail outlets, typically manufactured by screen or digitally printing a design on a pre-perforated self-adhesive vinyl assembly, have been in widespread use since 1993. U.S. Pat. No. 5,609,938 (Shields) and U.S. Pat. No. 5,773,110 (Shields) both disclose a perforated clear facestock material and an additional solid backing liner which have been incorporated into products made and sold since September 1993 by Visual Technologis, Inc. of Pineville, N.C. USA, as evidenced and available for public inspection in the reissue of U.S. Pat. No. 5,609,938 (Shields) file Ser. No. 09/267,025 at the U.S. Patent and Trademark Office
GB2 118 096 (Hill and Yule), GB2 165 292 and U.S. Pat. No. 5,830,529 also disclose the edge alignment of superimposed layers, by means of applying layers to a projecting surface which automatically aligns their perimeters with the downstand edge of the projecting surface, and by means of a recessed surface which automatically aligns the layer perimeters to the upstanding edge.
International Patent Application WO98/43832 (Pearson) discloses the partial imaging of a transparent glass substrate by means of a perforated decal on a carrier. In PCT/GB98/00803, the word xe2x80x9cperforatedxe2x80x9d is used to mean having a plurality of holes, not limited to a process of piercing through a material.
PCT/GB98/00803 discloses and claims the methodology of heat release transfers being automatically applied and also discloses three methods of forming vision control panels using an unperforated ceramic heat release transfer. One of these methods is the combination of method 2 in GB2 165 292 with previously known ceramic ink heat release transfer technology. Another is GB2 165 292 method 4 (stencil method) in conjunction with previously known ceramic ink heat release transfer technology, which is used to transfer ink layers over a stencil printed directly onto a glass sheet. In addition, WO98/43832 discloses the selective application of a heat release layer to a ceramic ink heat release transfer carrier, intended to facilitate the selective application of ceramic ink to a sheet of glass as a means of manufacturing vision control panels. In all the methods of WO98/43832, the ceramic ink is removed from the transfer carrier by means of a uniform layer of heat-activated adhesive.
Contra Vision Supplies Ltd of Stockport, UK and Precision Studios developed a process of using unperforated ceramic ink transfers by a combination of GB2 165 292 methods 2 and 1, the latter as improved by the xe2x80x98Through Combination Methodxe2x80x99 of WO97/15433 (Hill), and a resultant vision control panel was placed in the public domain in the USA and Austalia in March 1998 and exhibited at the Glastec ""98 exhibition in Dusseldorf, Germany, in September 1998.
GB2 165 292 method 1 and the xe2x80x98Through Combination Methodxe2x80x99 of WO97/15433, as used to make these disclosed panels, do not produce a design superimposed on a silhouette pattern with substantially exact registration. These combined methods of partially imaging a substrate enable an acceptable vision control panel to be made in spite of the errors in registration of conventional methods of printing, such as screenprinting.
While vision control panels having multiple layers of ink in substantially exact registration can be made by means of perforated transfers, the method has the disadvantage of the reduction in strength of the perforated material caused by the holes. During the transfer process, this leads to difficulties in applying the perforated decal or perforated decal and perforated decal carrier to a sheet of glass, the transferred material being liable to rupture and folding, both of which spoil the finished appearance of the panel. Additionally, such difficulties severely limit the size of perforated material that can be transferred to a sheet of glass. Also, the perforation of ceramic ink decals by mechanical punching is expensive because the punching tools become relatively worn because of the presence of glass xe2x80x98fritxe2x80x99 (finely ground glass) in the ceramic ink.
The stencil method disclosed in WO98/43832 has the disadvantage of requiring the separate process of the application of the stencil pattern to a sheet of glass prior to the application of the transferred ceramic material. Printing directly onto glass is a cumbersome and time-consuming process, primarily owing to the difficulties of handling heavy glass panels. Transfer processes of printing on glass have been developed and adopted for this reason and because it is possible to print successive applications of ink in better registration onto a decal carrier than onto a large sheet of glass.
The selective application of a heat release agent to a ceramic ink heat release transfer carrier, as disclosed in WO98/43832, does not result in a practical process. The heat applied to the paper surface to melt the heat release agent and activate the heat-activated adhesive on the other side of the transfer must heat all the heat-activated adhesive. The desired ink is supposed to be selectively transferred to the glass, leaving the unwanted ink on the transfer carrier. No indication is given as to how this method is supposed to work. The heat-activated adhesive is uniformly applied over the ceramic ink on the transfer and the heat is uniformly applied in the transfer machine by heated roller and optionally by pre-heated glass and therefore the adhesive uniformly adheres the ink to the glass. The adhesion of the ceramic ink to the carrier and the internal adhesive strength of the ceramic ink would need to be sufficient to enable an ink fracture mechanism and to overcome the adhesion of the ink to the glass outside the areas of the heat release agent in order for ink that is unwanted on the substrate to be retained on the decal carrier. Even assuming this method could be made to work, in spite of the overall layer of heat-activated adhesive, the resultant edges of the transferred pattern would be irregular owing to xe2x80x9cunderbreakxe2x80x9d or xe2x80x9coverbreakxe2x80x9d of ink from the fracture inducing edges of the heat release agent, which are remote from the glass surface.
JP63071385 (Dai Nippon) (abstract) discloses the transfer of superimposed ink layers from a transfer base material onto a transparent substrate by means of xe2x80x9cheat-adhesive transparent resin inkxe2x80x9d. This adhesive material forms part of the resultant panel and separates the ink layers from the substrate and this prior art does not disclose or relate to ceramic ink transfers.
Known methods of transfer include:
(i) indirect methods, for example waterslide transfers and indirect heat release transfers, and
(ii) direct methods, for example direct heat release transfers.
A transfer process comprises material to be transferred, commonly referred to as a decal (abbreviation of decalcomania), being transferred from a transfer carrier, commonly referred to as a decal carrier, onto a substrate surface.
An indirect transfer method is one in which the means of release of the decal from the decal carrier and the means of adhering the decal to the substrate are typically combined in a single layer on the transfer carrier. The decal is first removed from the carrier and then positioned on the substrate.
For example, a ceramic ink waterslide transfer typically comprises a mass-produced decal carrier, typically a specially prepared paper with a sealant layer and a water-soluble adhesive layer. This is optionally printed or otherwise coated with a downcoat, typically a methyl methacrylate based lacquer. It is then printed with the desired layers of ceramic ink or vitreous enamel ink forming the required image and then a covercoat is applied, typically a methyl methacrylate based lacquer. This transfer assembly is typically soaked in water and the decal comprising the covercoat, ceramic ink, optional downcoat and some adhering water-soluble adhesive is released from the carrier and then applied by hand to the substrate surface to be decorated.
As another example, an indirect ceramic ink heat release transfer typically comprises a mass-produced decal carrier, comprising a paper, a sealant layer, a combined heat-activated release and adhesive layer, typically a modified wax incorporating an adhesive or tackifire blend. This is optionally printed or otherwise coated with a downcoat, typically a methyl metcacrylate lacquer. It is then printed with the desired layers of ceramic ink and then a covercoat is applied, typically a methyl methacrylate based lacquer. The decal is then released by applying heat, typically by a heated steel plate under the paper, which activates the release/adhesive layer and allows the decal to be removed from the carrier and then be transferred to and adhered to the substrate to be decorated.
A direct transfer method is one in which a transfer assembly is applied directly to a substrate and the decal carrier is released and removed, leaving the decal on the substrate.
For example, a direct ceramic ink heat release transfer typically comprises a mass-produced decal carrier comprising a paper, a sealant layer and a heat release layer, typically a polyethylene glycol (PEG) wax. This is optionally printed with a covercoat, typically a non-film-forming covercoat. It is then printed with the desired layers of ceramic ink. Any design is printed in reverse to its intended orientation from the ink side of the substrate. Then a heat-activated adhesive layer is applied, for example a methacrylate resin. This transfer assembly is then typically positioned directly against the substrate with the adhesive layer against the substrate surface. Heat is applied via the paper, which simultaneously activates the adhesive layer and the separate heat release agent. This enables the decal of adhesive, ceramic ink and any covercoat to be adhered to the substrate and be transferred from the carrier, the carrier being released and removed from the decal and substrate. The substrate may optionally be pre-heated.
The term covercoat and downcoat are always used in relation to their position with respect to the substrate, a covercoat being a layer over the ink on the substrate and a downcoat being a layer adhered to the substrate, underneath the ink on the substrate.
Typical substrates onto which ceramic decals are transferred include ceramic holloware, ceramic flatware, hollow glassware and flat glass.
Ceramic ink typically comprises glass xe2x80x9cfrit,xe2x80x9d metal oxide pigments and a binding medium of solvent, resin and plasticiser. Ceramic ink may contain an oil, such as pine oil. Ceramic inks can be opaque or translucent.
All the above transfer materials and methods are well known in the art.
Many automatic methods of decal application have been devised, for example all the mechanical processes, firing ovens and furnaces described in WO98/43832 were well known in the art before the priority date of that patent application.
After ceramic ink is applied to a normal sheet of flat glass, sometimes referred to as float glass and sometimes referred to as annealed glass, the printed sheet of glass is then typically subjected to a thermal regime of up to a temperature of typically 576xc2x0 C., which bums off all components of the ceramic ink other than glass frit and pigment and melts the glass frit and fuses the remainder of the ink onto the glass, typically followed by relatively slow cooling to anneal the glass once again, which process will be referred to as an ink fusing regime. Optionally, annealed glass substrates with ceramic ink can undergo a tempering or toughening regime, which involves raising the glass temperature to typically between 670xc2x0 C. and 700xc2x0 C., in which temperature range the glass is relatively soft, and then cooling it relatively quickly, typically by cold air quenching. This causes differential cooling of the glass sheet, the two principal surfaces solidifying before the core solidifies. The subsequent cooling and shrinkage of the core causes a zone of precompression adjacent to each principal surface. The physical strength properties of the glass sheet are fundamentally changed by this glass tempering or toughening regime, which imparts a considerably improved flexura strength to the resultant tempered or toughened glass.
Such a glass tempering or toughening regime may be carried out after a separate ink fusing regime or as one process, the ink being fused onto the glass as part of that one process.
With either the ink fusing regime or the glass tempering regime, any transfer process adhesive, covercoat, downcoat and ceramic ink medium are burnt off in the furnace and do not form part of the resultant panel.
According to the present invention, there is a method of imaging an imperforate substrate on a substantially uniform imaging surface of said substrate so as to provide said substrate with a print pattern, said print pattern comprising at least two superimposed layers of marking material, said print pattern comprising at least one of said at least two layers of marking material on first portions of said substrate and devoid of both of said at least two layers of marking material on other portions of said substrate, and said at least two superimposed layers of marking material having at least one length of common boundary within said print pattern, said method including applying at least two initial superimposed layers of said marking material onto a base layer and removing portions of said initial superimposed layers of said marking material from said base layer by means of a force selectively applied to said marking material being supported by said base layer at the time of said removing, and wherein said substrate has at least one substantially different material property to said base layer, and wherein at least one surface of said at least two layers of marking material is applied directly in contact with said imaging surface of said substrate.
In a first embodiment, the method includes applying at least two initial superimposed layers of said marking material onto a base layer and removing portions of said initial superimposed layers of said marking material from said base layer by means of a force selectively applied to said marking material being supported by said base layer at the time of said removing, transferring the marking material remaining on said base layer to said first portions of said substrate, and wherein at least one surface of said at least two layers of marking material is applied directly in contact with said imaging surface of said substrate.
In a second embodiment, the method includes applying at least two initial superimposed layers of said marking material onto a base layer, transferring said at least two initial superimposed layers of said marking material to said substrate by means of a force selectively applied to said marking material being supported by said base layer at the time of said removing, removing portions of said initial superimposed layers of said marking material from said substrate, and wherein at least one surface of said at least two layers of marking material is applied directly in contact with said imaging surface of said substrate.
In a third embodiment, the method includes applying a base layer to said imaging surface of said substrate, applying at least two initial superimposed layers of said marking material onto said base layer, removing portions of said initial superimposed layers of said marking material from said base layer by means of a force selectively applied to said marking material being supported by said base layer at the time of said removing, and wherein said base layer is removed from said substrate, and at least one surface of said at least two layers of marking material is applied directly in contact with said imaging surface of said substrate.
In a fourth embodiment, the method includes applying at least two initial superimposed layers of said marking material onto a substrate and removing portions of said initial superimposed layers of said marking material from said substrate by means of a force selectively applied to said marking material being supported by said substrate at the time of said removing, and wherein said substrate is transmuted by means of energy applied to said substrate such that the transmuted substrate has at least one substantially different material property to said substrate, and wherein at least one surface of said at least two layers of marking material is applied directly in contact with said imaging surface of said transmuted substrate.
The print pattern for a vision control panel is typically a pattern of dots, straight or curved lines or other plurality of discrete elements of marking material and/or a plurality of areas devoid of marking material, for example in the form of a grid, net or filigree pattern. The print pattern may be uniform or non-uniform, such as in a vignette pattern, for example as typically applied to vehicle windows.
There are many variants of this method. All include the process of applying to a base layer a plurality of initial superimposed layers of marking material xe2x80x9cblocked outxe2x80x9d or xe2x80x9csolidxe2x80x9d, meaning in continuous layers that require areas of marking material to be removed to form the desired print pattern. The initial continuous layers of marking material, typically printed ink, may be in many forms. For example, they may extend over the whole area of the print pattern and the portions to be unimaged within the print pattern. Two or more such layers may be superimposed and each layer may be of any material and of any colour or other property. Such layers may act as a background layer to a design. A design extending over only part of the area of the print pattern and comprising one or more continuous layers may be applied to one or both sides of one or more of such background layers. Such initial arrangements of marking material, typically ink, will typically be referred to hereinafter as initial layers of marking material or initial layers of ink.
It should be understood that the term marking material is intended to include any imaging material that is identifiable within the visible or non-visible spectrum, including ink, paint, toner, powder, metallic deposits, gaseous materials as in a dye sublimation process, photosensitive materials, heat sensitive materials and other materials which may be rendered visible or the visibility of which maybe amended by electricity or other energy source. The initial layers of marking material may be applied by any means, including dip-coating techniques, spraying, printing by any means such as screenprinting, offset litho printing, flexographic printing, gravure printing, any digital printing system, such as electrostatic, inkjet, thermal transfer, dye sublimation, photographic or thermographic systems or by vacuum metalization.
A base layer has a primary surface onto which the initial layers of marking material are applied and to which at least one of the layers of marking material is directly applied. The base layer may comprise a single homogeneous material, a plurality of layers of the same or different materials and may be a primary base layer comprising said primary surface and be adhered to a secondary base layer which is releasable from the primary base layer, optionally by an intermediate release layer. The secondary base layer may also comprise a plurality of layers. A base layer, a primary base layer or a secondary base layer may be in the form of a transfer carrier or decal carrier typically comprising a paper or other filmic material, to which is typically applied a sealing layer and a release layer and which may have on its other surface an xe2x80x9canti-blockingxe2x80x9d or anti-friction surface typically to prevent this surface in a roll or stack of unimaged or imaged decal carrier material becoming stuck to an adjacent surface.
The primary surface of the base layer may be the surface of a paper or filmic or sheet material, a sealing layer, a release layer, an adhesive layer, another coating layer for example a material which is disposable by any means including being capable of being xe2x80x9cburnt offxe2x80x9d in a furnace, being destroyed by any radiation such as UV radiation or being dissolved. The primary surface of the base layer may be an overall uniform layer or a partial layer, for example of marking material applied in a previous process. The base layer may be rigid, flexible, compressible, conformable and of any shape. The base layer may be capable of being transmuted or transformed into the substrate having a substantially different material property to the base layer, typically by the application of an energy source, such as thermal energy. For example a sheet of normal, annealed glass may undergo a thermal regime to convert it to tempered or toughened glass, as previously described, with a substantially increased flexural strength. As another example, a base layer material may be changed in visual appearance. Polyvinyl butyral film, which is commonly used to laminate glass, typically changes from a translucent material to a transparent material upon the application of heat and pressure in the glass lamination process.
The substrate has an imaging surface to which the print pattern of superimposed layers of marking material is ultimately or residually applied and is in direct and intimate contact with at least one of the layers of marking material. Substrate materials may be of any material or materials, in any external shape and internal structure, including homogenous, laminar or cellular structures. The substrate may be any suitable organic or inorganic material, for example, plastic sheet, plastic film, metal, paper, card, aerogel, composites such as carbon fibre reinforced resin, laminates of any of the above materials, or other organic or inorganic substance. Substrates may be pre-coated, for example with bonding agents, print receptive treatments or be partially metallised or completely metallised, for example to form a mirror, one-way mirror or other reflective surface. Substrates may comprise one or more layers of substantially uniform marking material.
The substrate may be rigid, flexible, compressible or conformable. The imaging surface of the substrate may be plane or curved, preferably of single curvature in any cross-section.
A transparent material is defined herein as one capable of transmitting light or other electromagnetic radiation so that objects or images beyond can be clearly perceived by the human eye or other device.
A translucent material is defined herein as a material which admits and diffracts light so that objects beyond cannot be clearly perceived.
An opaque material is defined herein as a material which is substantially impervious to the passage of light.
The terms transmute or transform as used herein mean to change form from one nature, form, condition, state or material property to another.
The term xe2x80x9cto transferxe2x80x9d means to shift or move from one surface to another.
Variants of the method, typically describing different ways of forming the initial superimposed layers of marking material and different methods of removing the unwanted marking material, include the following methods:
1.
A first group of methods include the Mechanical Removal of Unwanted Marking Material by a force selectively applied to initial layers of marking material.
1.+
In a first method initial superimposed layers of marking material are applied to a base layer. Unwanted ink is then mechanically removed to leave superimposed layers of marking material on the base layer in the desired print pattern with substantially exact registration. The base layer is then transmuted or transformed into the finished transmuted substrate with at least one substantially different material property. For example, a sheet of annealed glass is printed with initial superimposed layers of ceramic ink, at least one layer covering the glass in a layer to the outer edges of the required silhouette pattern. To manufacture one type of vision control panel according to GB2 165 292, the annealed glass is typically covered with a layer of black ceramic ink, then one or more layers of white ceramic ink and then printed with one or more design layers, each layer being cured by conventional means, for example by heat in an oven and/or air drying tunnel.
Ceramic ink typically comprises finely ground glass xe2x80x9cfritxe2x80x9d, a pigment material typically of metallic oxide, the frit and pigment bound by a medium of solvent, resin and plasticiser. In this initially cured state, the ink is still of a relatively soft texture, typically requiring heat treatment in a furnace to achieve its hardened state in a finished sheet of decorated glass.
The unwanted ink is then removed from the area to be transparent by mechanical means, which may include:
(i) scraping by a comb tool, for example replacing a squeegee blade on a screen printing bed,
(ii) scraping by an array of chisel blades, or
(iii) abrading by an array of abrading wheels or abrading nozzles, for example high pressure air nozzles.
xe2x80x83Such ink removal will typically leave a silhouette pattern of lines with the layers of ceramic ink in substantially exact registration. The annealed glass and ceramic ink then are subjected to a glass tempering or toughening regime including raising the glass temperature within the range of typically between 670xc2x0 C. and 700xc2x0 C., then cooling rapidly, typically by air quenching. This results in tempered or toughened glass with a zone of precompression adjacent to each of the two principal surfaces, the tempered or toughened glass having a substantially higher flexural strength than the annealed glass forming the untreated base layer.
1.2
A second method is similar to the first method, except that before mechanical removal of the unwanted marking material by one of the techniques described, the layers of marking material are first pre-cut, for example with an array of flat blades or circular disc blades. The blades are easily available, such as Stanley knife blades manufactured by Stanley Tools Ltd of Sheffield, UK, or alternatively may be specially prepared. In precutting a pattern of lines, it is preferable for the blades to be singly ground rather than double ground, for example at an angle of 20-45 degrees to the opposite unground surface of the blade, each blade then being used so that the unground side is applied to the edge of a line to be retained, the blade being positioned outside this line and the ground edge facing towards the portion of ink to be subsequently removed. Individual blades or groups of blades may be sprung or subjected to a hydraulic pressure to ensure that each and every blade is applied with appropriate pressure so as to cut through the ceramic ink. Such pre-cutting facilitates the removal of unwanted ink to clean cut edges of the required print pattern. Chisels or other scraping tools of less width than the pre-cut edges of a print pattern can be used and the membrane tensile strength of the ink ensures that the unwanted marking material is cleanly removed up to the pre-cut edges. With pre-cut edges, even relatively blunt tools can be used to remove the unwanted ink, including the end of steel wire.
1.3
A third method is similar to the first method, except that the substrate has a base layer of a different material applied to one surface, for example by coating, printing or lamination. The base layer to which the layers of marking material are then applied can have one or more uses, including:
(i) forming a transparent frangible or soft layer to assisting the complete removal of the unwanted coloured ink without leaving coloured residue on the portions to be transparent, or
(ii) forming a scratch resistant layer to protect the substrate, and/or
(iii) acting as a slip plane, or
(iv) acting as a raft to support the unwanted ink and thereby assisting its clean removal.
xe2x80x83In either case, the base layer may optionally be removed from the finished product, for example by a heat process which burns off the base layer.
For example, a sheet of annealed glass is coated with a base layer, for example of clear methyl methacrylate lacquer, preferably a non-film-forming coat. This is overprinted with initial superimposed layers of ceramic ink and the unwanted ink is removed, for example by one of the techniques in the first method. The base layer assists the removal of all of the unwanted coloured ink layers, as required to form the desired silhouette pattern. When subjected to an ink fusing or glass tempering regime, the base layer is burnt off leaving the desired layers of ceramic ink in substantially exact registration in the desired silhouette pattern, fused onto the glass substrate.
1.4
A fourth method is similar to the third method except that the initial superimposed layers of marking material and optionally the base layer are pre-cut as in the second method. It has been found that a non-filming-forming, semi-brittle base layer is particularly advantageous as a raft to the unwanted marking material, as described in item (iv) in method 1.3. Chisels or other scraping tools of less width than the pre-cut edges of a print pattern can be used and the membrane tensile strength of the ink and/or the supporting raft effect of the base layer ensure that the unwanted marking material is cleanly removed up to the pre-cut edges. As with method 1.2, relatively blunt tools including wire can be used to remove pre-cut unwanted marking material.
All the remaining method variants utilise transfer (decal) technology.
1.5
In a fifth method, unwanted marking material is mechanically removed from a transfer carrier. The remaining layers of marking material form the desired print pattern superimposed with substantially exact registration and are then transferred onto a substrate.
For example, to manufacture a vision control panel, a direct ceramic ink heat release decal carrier typically comprising paper and the paper preferably coated with a sealing layer and coated with a heat release layer such as a wax material, is optionally coated with a covercoat, preferably a non-film-forming frangible covercoat. It is then printed with initial superimposed layers of ceramic ink, typically comprising a background layer of one colour and another background layer of another colour. The ceramic ink layers are initially cured as in the conventional manufacture of ceramic ink transfers, for example by heat in an oven and/or air drying tunnel. Then the decal is typically coated with a beat-activated adhesive.
The ceramic ink which is unwanted in the finished vision control panel is selectively removed from the ceramic ink decal carrier, for example by one of the techniques in the first method, to leave superimposed layers of ceramic ink in substantially exact registration within the desired silhouette pattern. In this fifth method, when the unwanted ink is removed, the carrier paper or the surface sealing treatment of the carrier paper or optional covercoat under the ceramic ink is exposed between the lines of superimposed ink. The ceramic ink decal is then transferred to a sheet of glass, typically by passing the printed and processed transfer assembly through rollers with the sheet of glass, the roller adjacent to the transfer being heated and the glass optionally being pre-heated, as well known in the art.
In the case of a ceramic ink waterslide transfer, one or more layers of methyl methacrylate downcoat are optionally applied to the decal carrier, optionally followed by a non-film-forming frangible downcoat, before the initial superimposed layers of ceramic ink. Following the selective removal of unwanted ink, by mechanical means, a covercoat of methyl methacrylate lacquer is applied over the superimposed layers of ceramic ink and the exposed areas between, to provide a continuous film layer that will support the ceramic ink upon application of water, thereby enabling transfer of the ceramic ink decal from the decal carrier to a sheet of glass.
In the case of an indirect ceramic ink heat release transfer, the conventional process is followed up to and including the application of the initial superimposed layers of ceramic ink. Unwanted ceramic ink is then selectively removed by mechanical means to leave residual layers of ceramic ink in the layout of the desired print pattern followed by an overall application of a methyl methacrylate covercoat and normal transfer thereafter.
After such waterslide or heat release transfer of the ceramic ink in the desired superimposed layers in the desired silhouette pattern in substantially exact registration, subsequent heat treatment fuses the ceramic ink into the glass, which may optionally be heat treatment to form toughened glass, all as well known in the art and as previously described.
1.6
A sixth method is similar to the fifth method except that before the removal of unwanted marking material from the decal carrier, the edges of the required print pattern are first cut, for example with an array of flat knife blades or circular disc blades, as in the second method. This sixth method may also use either waterslide or indirect heat release or direct heat release transfer. For any indirect transfer, a downcoat layer should typically be film-forming, as this aids ink removal after it has been cut.
By selection of suitable materials, it has been found with ceramic ink transfers that the width of an individual chisel blade or other ink removal tool can be of less width than the width of the ceramic ink to be removed, which nevertheless is pulled away from the decal carrier to the full extent required, up to the precut lines. The membrane tensile strength of the ceramic ink and/or the tensile strength or supporting xe2x80x9craftxe2x80x9d effect of any downcoat or covercoat adjacent to the decal carrier ensure the ink to be removed holds together. As with methods 1.2 and 1.4, relatively blunt tools including wire can be used to remove the pre-cut unwanted marking material. This unexpected feature assists the setting up of such a production line, allowing a tolerance between the positioning of the pre-cutting blades and the edges of the chisels or other means of ink removal.
The scraped ink can then be efficiently disposed of, for example by blowing or suction.
2.
A second group of methods includes the use of a Heated Profiled Roller, which selectively applies an adhesive force on the initial superimposed layers of marking material.
2.1
In method 2.1, a heated profiled roller is used in conjunction with a direct transfer assembly to selectively remove unwanted marking material from initial superimposed layers of marking material on a decal carrier, leaving the desired print pattern of marking material layers to be transferred to the substrate by conventional means. For example, to manufacture a vision control panel, a direct ceramic ink heat release transfer is conventionally produced to incorporate initial superimposed layers of ceramic ink. The ink not required to be in the silhouette pattern is transferred by means of a heated, profiled roller from the decal carrier to the heated profiled roller, from which it is subsequently removed. The profiled roller has been cast, lathe cut, ground or otherwise formed with the negative of the required pattern projecting from its surrounding surface area or areas. For example, a profiled roller comprising an array of projecting cylindrical elements applied to the heat-activated adhesive surface will selectively remove lines of unwanted ink from the decal carrier by activating the adhesive across the width of the cylindrical elements and activate corresponding widths of release agent. For example, with the described direct ceramic ink heat release transfer assembly, within the width of an individual cylinder, of width approximating to that of the intended transparent lines, the heat-activated release layer will be melted and the heat-activated adhesive converted to its adhesive state, thus removing the unwanted width of ceramic ink from the decal carrier onto the individual cylinder. A scraping blade subsequently removes the unwanted ink from each cylinder of the heated roller. By conventional transfer means, the lines of ceramic ink remaining on the decal carrier are transferred from the decal carrier to a sheet of glass. The transferred ceramic ink and glass then undergo a heat treatment process, such as one of those previously described, to fuse the ceramic ink onto the glass.
2.2
Method 2.2 is similar to method 2.1 except that the edges of the desired print pattern are pre-cut, as in the sixth method, 1.6. For example, using a direct ceramic ink heat release transfer, the layers of heat-activated adhesive, ceramic ink and, optionally, a downcoat are all pre-cut. The cylindrical elements can advantageously be narrower than the pre-cut widths of unwanted ink and still remove all the unwanted width of ink, owing to the tensile membrane strength of the decal layers. This feature assists the setting up of a production line with reasonable tolerances between the pre-cutting and ink removal stages.
2.3
In method 2.3, a heated profiled roller is used to selectively transfer the desired print pattern of marking material onto a substrate from a direct transfer decal carrier. For example, to make a vision control panel, a conventional direct ceramic ink heat release transfer carrier is printed with initial superimposed layers of ceramic ink, as in method 2.1. The ink required to be in the silhouette pattern is transferred to a sheet of glass by means of a heated, profiled roller that has been cast, lathe cut, ground or otherwise formed with the required silhouette pattern projecting from its surrounding surface area or areas. For example, a profiled roller comprising an array of projecting cylindrical elements will selectively apply the required heat process to the transfer and thus transfer a pattern of superimposed ceramic ink lines to the sheet of glass. Within the width of an individual cylinder, of width approximating to that of the intended line of ceramic ink, the heat-activated release layer will be melted and the heat-activated adhesive converted to its adhesive state, thus adhering the desired width of ceramic ink to the glass. The adhesive force between the adhesive lines and the glass and the adhesive lines and the ink surface pulls away the desired lines of ceramic ink from the carrier by means of the ink fracturing either side of each line and the unwanted ink between lines of the silhouette pattern being removed on the carrier by the carrier being pulled away from the glass. Thus, an array of lines is transferred from the ceramic ink decal carrier to the glass by the selective adhesive force exerted on the surface of the ceramic ink remote from the decal carrier, in a pattern of lines. The transferred ceramic ink and glass then undergo a heat treatment process, such as one of those previously described.
2.4
Method 2.4 is similar to method 2.3, except that the heat-activated adhesive layer, the initial superimposed layers of marking material and, optionally, the heat release agent are pre-cut, for example by one of the methods in the sixth method, which removes the need for the marking material fracture mechanism required in method 2.3. In the example production of a vision control panel, the projecting roller cylinders can be of narrower width than the ink to be transferred, the tensile membrane strength of the ink layers being sufficient to pull the ink from the whole width required to be transferred up to the pre-cut lines. This arrangement assists the setting up of such a production line, allowing a tolerance between the positioning of the cutting blades and the edges of the individual cylinders on the heated, profiled roller.
2.5
Method 2.5 is similar to method 2.3, except that the heat-activated adhesive is selectively applied to the marking material in the form of the desired print pattern, which assists the accurate production of the desired print pattern. For example, in the production of a vision control panel, the required ink fracture mechanism of ceramic ink on a direct ceramic ink heat release transfer is initiated at the edges of the heat-activated adhesive printed in the form of the desired silhouette pattern. This allows the ceramic ink to be transferred onto a sheet of glass, in the desired silhouette pattern. The desired vision control panel is completed following a previously described heat treatment regime.
3.
A third group of methods relies on the selective application of the adhesive layer in a transfer assembly, to define the desired print pattern and apply a selective force onto the initial superimposed layers of marking material to form the required print pattern.
3.1.
In method 3.1, selective application of both the adhesive layer and release layer on a direct transfer effects the transfer of the print pattern only from the decal carrier. For example, to produce a vision control panel, the heat release agent in a direct ceramic ink heat release transfer assembly is selectively applied to the decal carrier in the form of the desired silhouette pattern of the vision control panel. The initial superimposed layers of ceramic are then applied and the heat-activated adhesive layer is also selectively applied in the form of the desired silhouette pattern, in as close register as possible to the selectively applied heat release agent. Normally decal carriers are constructed to facilitate ink removal. However, in this case a layer of ink adhesion enhancer or bonding agent is advantageously selectively applied between the selectively applied release layer or is applied continuously under or over the selectively applied release layer. When the direct ceramic ink heat release transfer is passed through a conventional transfer machine, the ceramic ink forming the desired silhouette pattern is simultaneously adhered to the glass and released from the carrier and transfers to the glass sheet. The unwanted ink remains on the decal carrier by means of an ink fracture mechanism along the edges of the silhouette pattern. The ceramic ink and glass then undergo an ink fusing or glass tempering heat regime.
3.2
In method 3.2, only the heat-activated adhesive is selectively applied over the initial superimposed layers of marking material in the form of the desired print pattern, the heat release layer being continuous across the decal carrier. For example, heat-activated adhesive is selectively applied onto the initial superimposed ceramic ink layers of a direct ceramic ink heat release transfer. When the ceramic ink heat release transfer is passed though the transfer machine all the release layer is activated, allowing the removal of all of the initial superimposed layers of ink from the carrier by the adhesive force exerted by the selectively applied adhesive, onto the glass. The force to remove the ceramic ink is selectively applied to the ceramic ink surface remote from the transfer carrier. At this juncture, or after heat treatment up to less than the temperature that would incur bonding of the ceramic ink to the glass, the unwanted ink between the selectively applied adhesive can be removed by a number of methods, such as air jetting or water jetting or the application and removal of self-adhesive tape. The bond of the heat-activated adhesive to the glass is sufficient to retain the ink adhered to it, while the ink ruptures at the edges of the heat-activated adhesive, thus defining the edges of the silhouette pattern and allowing the removal of unwanted ink.
3.3
Method 3.3 is similar to method 3.2 except that the selectively applied heat-activated adhesive forms a stencil of the desired silhouette pattern, such that when the glass and the initial superimposed layers of ceramic ink are subjected to sufficient temperature to bake the ink onto the glass or to fuse the ink into the glass, the stencil formed by the heat-activated adhesive acts as a barrier against such adhesion and/or fusion. The ceramic ink outside the stencil, inside the desired silhouette pattern, is baked onto the glass or is fused onto the glass, as required. There are several alternative means of enabling the removal of the stencil and the ceramic ink above it. For example, an expansive agent can be incorporated within the stencil, thus bursting off the ink above the stencil, for example during a thermal cycle, or the stencil allows the removal of the stencil and the ink above it, for example by air jetting or water jetting or the application and removal of adhesive film. When the unwanted ink has been removed, a further heat regime may be required in order to fuse the ink into the glass and, if required, toughen the glass.
While methods 3.1, 3.2 and 3.3 have been described in relation to direct transfers, methods 3.2 and 3.3 can be practised with indirect transfers having a continuous release layer adjacent to the decal carrier, then a selectively applied adhesive layer, which is then overprinted with the initial superimposed layers of marking material, then preferably a covercoat in the case of ceramic ink transfers, typically a methyl methacrylate lacquer.
4.
A fourth group of methods utilises a direct transfer with a stencil of the desired print pattern printed over the initial superimposed layers of marking material and adhesive, the adhesive exposed between the stencil portions exerting a selective force to remove layers of marking material from the decal carrier.
4.1
In method 4.1, a beat-activated adhesive is applied in a continuous layer over the initial superimposed layers of marking material on a direct transfer and an additional stencil layer is selectively applied to the heat-activated adhesive surface, the stencil being the negative of the desired print pattern. The heat release layer is also selectively applied but in the form of the required print pattern. On undergoing a conventional transfer process, the desired print pattern is selectively transferred to the substrate. For example, using a direct ceramic ink heat release transfer, the ceramic ink layers rupture along the edges of the silhouette pattern owing to the adhesive force selectively applied outside the stencil area with corresponding release from the decal carrier. The unwanted ink is retained on the decal carrier along with the stencil material.
4.2
Method 4.2 is similar to method 4.1, except the release layer is continuous, allowing the whole of the decal to transfer to the substrate. Upon transfer, the selectively applied stencil layer prevents the adhesion of the transferred decal above the stencil pattern to the substrate, thus enabling the removal of the stencil and the marking material above it immediately following this process or after a further heat regime, as described in method 3.3. In the making of a vision control panel, the initial superimposed layers of ceramic ink are removed from a decal carrier by the force of the heat-activated adhesive selectively applied to the ceramic ink surface remote from the carrier, outside the stencil pattern. The unwanted ink and the stencil are then removed, for example by air jetting or water jetting immediately after transfer or after a further heat process. The panel with the required silhouette pattern of ceramic ink is then subject to an ink fusing or glass tempering regime.
4.3
Method 4.3 is similar to method 4.2 except that the stencil is applied between the ceramic ink layers and the adhesive layer.
5.
A fifth group of methods utilises a stencil of the required print pattern applied to a decal carrier before applying the initial superimposed layers of marking material.
5.1
In method 5.1, a stencil of the required print pattern is applied to a decal carrier of either a direct or indirect transfer, before application of the initial superimposed layers of marking material. The stencil and the unwanted marking material are removed before transfer of the desired layers of marking material in the desired print pattern onto the substrate.
For example, a waterslide ceramic ink decal carrier is optionally first printed with one or more layers of downcoat, typically a methyl methacrylate downcoat to increase the strength of the resultant decal. A heat expandable stencil is printed, being the negative of the desired silhouette pattern of a vision control panel. The initial superimposed layers of ceramic ink are then printed and the decal is subjected to a temperature that will cause the stencil to expand and xe2x80x9cburst offxe2x80x9d the ink directly above it, which is removed along with the stencil material, for example by air jetting or by vacuum. A covercoat of methyl methacrylate based lacquer is then applied overall the transfer, and the ceramic ink decal comprising the covercoat, the required layers of ceramic ink in the desired print pattern and any downcoat are then transferred to a sheet of glass in the normal manner. The unwanted ink is removed by the selective force exerted by the stencil expanding.
Alternatively, the stencil may be a perforated material. For example, a perforated self-adhesive film assembly typically comprising a polyvinyl chloride film facestock material, a pressure-sensitive adhesive and a release liner are perforated to leave a perforated facestock, a perforated adhesive layer and a perforated liner.
The perforated liner is removed and replaced with a conventional decal carrier having a release surface, this assembly falling with the invention of U.S. Pat. No. 5,858,155. In the case of an indirect, waterslide ceramic ink transfer, an optional downcoat of methyl methacrylate and the initial superimposed layers of ceramic ink are then applied over the perforated material. The perforated self-adhesive vinyl is then removed with the ceramic ink immediately above it. A covercoat, typically of methyl methacrylate, is then applied over the ceramic ink and area from where the ceramic ink has been removed. This assembly is then wetted to enable transfer of the decal to a sheet of glass. In the case of a direct ceramic ink transfer, a heat-activated adhesive layer is applied over the initial superimposed layers of ceramic ink before the perforated self adhesive vinyl stencil is removed with the ceramic ink and heat-activated adhesive directly above it. Alternatively, a downcoat in the case of an indirect transfer or a topcoat in the case of a direct transfer can be applied to the decal carrier before the application of the perforated film stencil to the decal carrier, this layer typically of methyl methacrylate assisting the transfer of the complete decal after removal of the unwanted ink.
The decal is transferred to a glass sheet in a conventional manner and the ink is fused onto the sheet of glass.
5.2
In method 5.2, a stencil of the required print pattern is printed onto a direct or indirect decal carrier and transferred with the initial superimposed layers of marking material onto the substrate. The stencil and the marking material immediately above it are then removed to leave the desired layers of marking material in the required print pattern with substantially exact registration. For example, to manufacture a vision control panel, a stencil is printed onto the water soluble gum of a waterslide transfer, before printing the initial superimposed layers of ceramic ink and a methyl methacrylate lacquer covercoat to assist transfer. The stencil therefore lies under the initial superimposed layers of ceramic ink after transfer to a sheet of glass. When the glass is subjected to a heat regime, the stencil prevents the ceramic ink bonding to the glass. The stencil may optionally be expansive under heat and burst off the ink above it. Alternatively, the stencil and unwanted ink are removed, for example by air jetting or water jetting or by the application and removal of self-adhesive tape or other means, to leave superimposed layers of ink in substantially exact registration within the desired silhouette pattern.
The ceramic ink decal is removed from the decal carrier, after wetting the transfer, preferably by the selective application of a force throughout the area of the decal, typically by means of suction through an array of small holes in a suction apparatus that assists the transfer process, especially valuable when used with transfers of relatively large area, say above 0.5 m2 area. A suitable suction device is described later.
6.
Method 6 relates to an improvement of existing methods using a perforated base layer, such as disclosed in GB2 165 292 and also disclosed in U.S. Pat. No. 5,030,529. In this method, a decal carrier has initial superimposed layers of marking material applied to it and the decal carrier and layers of marking material are then perforated together. For example, to manufacture a vision control panel, a ceramic ink decal carrier is printed with initial superimposed layers of ceramic ink and the carrier and ceramic ink are then perforated. The perforated ceramic ink is then transferred to a sheet of glass.
In the case of a ceramic ink waterslide transfer, a downcoat would typically be applied to the decal carrier before the initial superimposed layers of ceramic ink, to improve the transferability of the decal. As a further improvement to the prior art method, the ceramic ink is overprinted before perforation with one or more covercoats of clear methyl methacrylate lacquer, to provide increased strength to the perforated decal, to allow it to remain dimensionally stable and be positioned accurately on the glass sheet.
In the case of a direct ceramic ink heat release transfer, the perforated ceramic ink being transferred is supported by the perforated paper carrier. However, one or more layers of downcoat, typically of methyl methacrylate, will assist the clean perforation of the ceramic ink.
In accordance with the improvement of the present invention, one or more additional binding layers, typically of methyl methacrylate lacquer, may be applied intermediate the layers of ceramic ink to aid clean perforation of the holes and/or effective transfer to the glass. The ceramic ink itself may optionally contain a higher proportion of resin and/or plasticiser, again to assist perforation and/or transfer.
Alternatively, the decal carrier, whether for direct or indirect transfer, is perforated before applying the ceramic ink layers. An improvement to this method comprises the use of a saturated paper or other substantially non-porous filmic material, to prevent absorption by exposed perforated paper of printed ink constituents.
Also, in accordance with the present invention, the transfer process may be assisted by a layer of unperforated material, such as a low-tack self-adhesive vinyl strengthening the perforated transfer material. In the case of an indirect transfer, this is preferably applied to the perforated covercoat or perforated ink, reinforcing the perforated decal. Also preferably, the self-adhesive vinyl is supported by a suction deck as described herein, while the wetted decal carrier is peeled off from the decal and self-adhesive vinyl. The decal and self-adhesive vinyl are then transferred to the substrate, optionally by a suction deck as described herein, and the self-adhesive vinyl is then peeled off the decal which remains on the substrate. In the case of a direct transfer, the unperforated material is applied to the side of the perforated decal carrier remote from the ink, thus facilitating the direct transfer of the decal, for example by means of the suction deck described herein.
After transfer of the perforated decal, the glass and ceramic ink are then subjected to a thermal regime, typically to fuse the ceramic ink into the glass, optionally to form toughened glass, all as previously described.
It should be understood that the above method variants are examples and are not limiting.
In any of the above methods, the initial superimposed layers of marking material may contain one or more design layers. A design layer does not extend over every portion of the print pattern. The term design layer includes one or more xe2x80x9cspotxe2x80x9d colour layers, a multi-colour printing process such as a four colour process, a five colour process or a hexachrome process, or a combination of any of these, for example a four colour process with an additional one or more xe2x80x9cspotxe2x80x9d colour layers. The marking material layers can be applied by any means, for example coated, screenprinted, litho printed, digitally printed, for example by a digital ink jet printer, sprayed or air bushed.
In all the above methods using ceramic ink, it can be advantageous to introduce one or more interlayers of clear glass flux or glass frit with a clear medium, typically of solvent, resin and plasticiser (essentially a clear ceramic ink with no pigments), to separate layers of differently coloured ceramic ink, to reduce the risk of these becoming intermixed during firing. Such additional interlayers are particularly beneficial between the black and white and white and coloured layers used to form vision control panels, to assist the production of separate, opaque ceramic ink layers. It can also be advantageous to introduce single or multiple layers of covercoat and/or downcoat and/or one or more binding layers between successive layers of marking material, to assist decal transfer, perforation or other decal treatment. U.S. Pat. No. 5,830,529 and WO98/43832 only refer to producing perforated layers of ceramic ink, in which the ink is interconnected and thus has an overall tensile or membrane strength. The methods outlined herein enable the production of dot, line and other print patterns comprising discrete elements which may be held in the desired spatial relationship and satisfactorily transferred in large size transfers, even considerably greater than the industry standard of typically 80 cmxc3x9760 cm.
While the above methods are described principally in relation to ceramic ink transfers, they are applicable to the transfer of other types of marking material, onto glass or other substrates, such as the transfer of organic inks onto plastic sheet materials, a subsequent curing regime or heat treatment being typically applied to suit the particular type of ink and substrate.
Also, it should be understood that the invention is applicable to other permutations of known transfer technology, for example a direct transfer could have a water-soluble adhesive and a water-soluble release layer, or a heat-activated adhesive and a water-soluble release layer, or a water-soluble adhesive and a heat-activated release layer. In the case of a direct transfer with a water-soluble adhesive and a water soluble release layer, the adhesive can be first activated and then the release, or both can be simultaneously activated with differential tack, which can be provided by the selection of appropriate adhesives or the pre-heating of the substrate, such that the decal carrier can be removed while the decal remains on the substrate. The invention also applies to other means of decal adhesion or release. For example, the adhesive could be a pressure-sensitive adhesive.
Stencil materials used in any method variant may have characteristics to assist removal, for example under heat, UV or other initiator or activator, the stencil may expand, shrink, degrade, melt or be vaporised, to assist the removal of the stencil and the unwanted ink above it. For example, a stencil of gum arabic will shrink under heat, thus facilitating the removal of the unwanted ink above and the stencil itself.
As another example, the stencil material may be volatile at a temperature below that required to bond and/or fuse ceramic ink to glass, the change in state bursting off the unwanted ink in a pre-heat treatment, the disturbed ink then being completely removed, for example by vacuum, brushing, air jetting or water jetting.
A whole range of micro-encapsulation technology is applicable for:
(i) adhesives, for example lubricants to enable the adhesive to be relocatable,
(ii) transfer release mechanisms, and
(iii) stencil materials in any of the above method variants, for example encapsulated blowing agents.
The micro-encapsulations are typically opened by one of a range of initiators, such as pressure, heat, solvent, UV, infrared or exposure to visible light. For example, layers adjacent to one side of a glass sheet may be subject to UV rays from the other side of the glass sheet, for example for selective curing of UV ink through a mask of the required silhouette pattern on the one or other side.
Catalytic components may also be located on surfaces to be joined by transfer process or be in different micro-encapsulations on the same surface or be mixed prior to use. Such technologies may be used for many purposes, for example to create overall or selective adhesion, stencil barriers to adhesion, the curing of inks and the release of decal carriers.
For simplicity, the production of a print pattern of straight lines has been typically described in the above methods. However, a variety of print patterns is possible with any of these methods. For example, the ink removal methods 1.1 to 1.6 can be used to remove lines of ink in orthoganal directions to achieve a print pattern of discrete rectangles. Oscillating chisels and, where appropriate, oscillating knife blades can produce curved line print patterns. Alternatively, the ink on a transfer carrier can be pre-cut by laser to any desired print pattern, prior to the removal of unwanted ink. Laser cutting can be assisted by the incorporation of a reflective material, such as a metal foil, on the decal carrier. This enables an optical laser to monitor and control the depth being cut by a cutting laser, reflected light from the optical laser indicating that the required depth of cut has been reached, enabling it to control the cutting laser accordingly. This dual laser technology is well known. In methods 2.1 to 2.5, the heated roller defining the print pattern can have a projecting pattern of curved lines, dots or other discrete areas or have an interconnected surface with a plurality of recesses. In methods 2.5 and 3.1 to 3.3, the selectively applied adhesive can be printed or otherwise applied in patterns other than a line pattern, for example a pattern of dots or other discrete areas or in an interconnected pattern such as a grid, net or filigree pattern. In methods 4.1, 4.2, 5.1 and 5.2, the stencil material can be applied in any pattern including lines, dots or other discrete areas or an interconnected pattern.
A novel form of suction apparatus suitable for transferring ceramic ink or other types of transfer or decal comprises a lightweight, high strength, stiff, xe2x80x9cstressed skinxe2x80x9d structure typically comprising two plane parallel sheets of material forming upper and lower xe2x80x9cskinsxe2x80x9d, having a high strength-to-weight ratio, for example formed from carbon fibre reinforced resin or glass reinforced resin or aluminium or titanium or acrylic. A cellular web core construction connects the two skins, typically in the form of a square, triangular or honeycomb grid of plane webs, which results in an extremely stiff construction. The apparatus is typically used to transfer filmic material onto the surface of a substrate, such as a horizontal sheet of glass. The web members have voids sufficient to provide interconnected cells of air forming an air plenum, the perimeter remaining sealed. The lower skin is perforated with an array of small holes and a suction pump is connected to the plenum such that a suction force can be exerted through each hole in the lower skin onto a surface over which the perforated lower skin is placed, upon the operation of the suction pump. Such a suction apparatus may be termed a xe2x80x9csuction deckxe2x80x9d. The thickness of the suction deck, typically 10-30 mm, is primarily designed to suit the skin material and plan dimensions of the suction deck. Similar suction arrangements are known in the art of screen printing machinery, forming a screen printing suction xe2x80x98bed,xe2x80x99 their purpose being to hold down a substrate while the screen printing squeegee is being operated, to prevent movement of the substrate caused by the squeegee action. The suction deck of the present invention acts in the opposite direction, as a lifting device. The suction deck is positioned above and directly onto a material to be transferred and, by the application of a partial vacuum, the pressure of the air in the plenum is reduced below ambient air pressure. The suction deck then forms an effective means of lifting, for example a decal from a waterslide decal carrier or the whole of a direct transfer assembly, which can then be repositioned onto a substrate.
In the case of a ceramic ink waterslide transfer, the removal of the ceramic ink from the decal carrier is effected by the selective application of force at the surface remote from the carrier, typically suction applied through circular holes in a regular layout on the suction deck. The holes are typically small, say 0.1-1 mm diameter, to avoid undue deformation at the hole positions of the transferred ceramic ink and any covercoal More than one covercoat layer is optionally beneficial, for such means of transfer, to build up sufficient membrane strength to avoid undue distortion within the suction holes that could otherwise leave air holes between the transferred ceramic ink decal and glass at these positions. An alternative means of eliminating this potential problem is to add a layer of material with a microporous, open-cell, air permeable structure to eliminate the concentrations of suction force at hole positions in the lower skin. After the application of the suction force to the side of the decal remote from the transfer carrier, the transfer carrier is wetted and the carrier paper peeled away. Conventional indirect decals are dimensionally unstable after removal from the decal carrier, especially for large decals of greater than say 80 cmxc3x9760 cm. The suction deck maintains the dimensional stability of the decal throughout the transfer process.
The suction deck may be easily manhandled, being of lightweight construction, and thus accurately located over the glass. Alternatively, it may be attached to a robotic arm or x-y plotter device, for example to enable the automatic and accurate positioning of a decal onto a sheet of glass. The suction deck may be used to particular advantage in conjunction with glass handling equipment, such as is typically used to enable the accurate drilling of holes in sheets of glass. A glass sheet can be automatically moved on a roller bed to a desired position, controllable to great accuracy. Use of an accurately and automatically positionable suction deck with such existing automatic glass handling equipment provides a much more accurate and economic solution to the positioning of decals onto large sheets of glass than existing manual techniques or automatic roll-to-roll techniques. These benefits apply especially to the application of decals onto large sheets of glass, for example of width greater than 1.2 m (4 ft). Typically, an optical device will xe2x80x9creadxe2x80x9d the location of two reference points printed onto a decal and transmit this information to a controlling computer which can then position the suction deck and supported decal to the required position over the glass, according to pre-entered co-ordinate data. When it is required to release the decal onto the glass, the air pressure inside the plenum is changed to positive air pressure, greater than the ambient air pressure. Decals can be aligned on a sheet of glass to a tolerance of less than 3 mm (xe2x85x9xe2x80x3), enabling xe2x80x9ctilingxe2x80x9d of decals, to cover large overall areas. Such stressed skin constructions arc extremely stiff. Whatever the arrangement to support the suction deck, it will typically be designed to have a maximum relative deflection between any two points on the suction deck lower surface of less than 3 mm, preferably less than 0.5 mm, when loaded with the material to be transferred. The lower skin may optionally be constructed with a small, concave precamber to ensure that transferred material is applied from its centre outwards.
This type of suction deck apparatus can also be adopted for the application of direct transfers, in which the decal is retained on the decal carrier until the decal is applied to the surface of the substrate. For the application of heat release transfers, hot air is introduced into the plenum to activate the heat release agent and heat-activated adhesive. Alternatively the suction deck may be heated by other means, for example conduction through a suitable skin material, such as aluminium. The substrate, for example glass, may optionally be preheated. If the suction deck is suitably supported, overall pressure can also be applied to the transferred material. Optionally, radiant heat may subsequently be applied, preferably onto a decal carrier having a black surface on the side remote from the ceramic ink. Alternatively, a glass sheet and pre-positioned decal may be passed through heated rollers before removing the transfer carrier.
Optionally, the suction deck is equipped with a vibrating device, for example comprising an eccentrically weighted rotating element, for example driven by electric motor attached to the structure of the suction deck. The resultant vibration assists release of one surface from another, for example of a suction held decal from its carrier.
Perforated decals can be handled by the suction deck after the addition of a non-perforated layer to the perforated decal carrier and/or decal to be transferred, the non-perforated layer typically being a self-adhesive film material.
All the above methods numbered 1.1 to 6 are advantageous over the prior art. They are unified by the means of removing marking material from a base layer by means of a selectively applied force over the area of the base layer. The force is applied by a means which does not form a substantial part of the resultant partially imaged substrate. This selectively applied force typically defines the print pattern.
The above methods are all advantageous over the stencil method of WO98/43832, which requires the printing of two different surfaces, a decal and a sheet of glass, as well having the handling difficulty and relative inaccuracy of printing a pattern onto glass, particularly if the glass is of large size.
The WO98/43832 method of selective application of beat release agent within a heat release transfer is clearly impractical, as previously described, and would not enable an accurate silhouette pattern to be formed. Even if a combination of ink strength, adhesion of the heat-activated adhesive to the glass and ink and adhesion of the ink to the carrier could be found to make the method work, the force to remove the ink from the carrier would be uniformly (not selectively) applied by the uniform layer of adhesive, leading to an imprecise print pattern.
Thus all the methods described distinguish and distinguish advantageously over the prior art methods.